Radio-frequency tuning device



Dec. 2, 1958 H. T. LYMAN ET AL 2,863,129

RADIO-FREQUENCY TUNING DEYICE Filed Feb. 9. 1954 ATTORNEYS.

l lnited States Patent ice p 7 v PatentedDec. 2, 1958 the top of a brass sleeve 14 having a deep slot 15 extending upward from its bottom edge. If desired, the 2863129 junction between cap nut 19 and the brass sleeve 14 RADIO-FREQUENCY TUNING DEVICE Harold T. Lyman, Milford, Conn., and Lester E. Hill,

Nashville, Tenn., assignors to Aladdin Industries, Incorporated, Nashville, Tenn., a corporation of Illinois Application February 9, 1954, Serial No. 409,028

2 Claims. 01. 336-75) This invention relates to radio-frequency tuning devices; in particular, it relates to a novel tuned coil char- I has all the functional advantages of the familiar coils having movable cores while being far simpler and cheaper to manufacture.

It is accordingly the major object of the present invention to provide a tunable coil wherein tuning is accomplished by means of relative movement between the coil and its own mounting clip, thus eliminating the necessity for a movable core and supporting structure therefor.

Another object of the invention consists in providing a tuned radiofrequency inductor which can be conveniently mounted in a small chassis aperture and tuned from above the chassis, although being for the most part located below the chassis.

Still another object of the present invention is to provide a tunable coil adapted for below-chassis mounting and above-chassis tuning which is particularly well suited for use as a tuning coil in television I.F. amplifiers.

Other objects and advantages of the present invention will appear as the specification proceeds.

In the accompanying drawing we have illustrated a typical embodiment of our invention. Figure 1 is a side elevation view showing a coil embodying the invention. Fig. 2 is a sectional view of the Fig. 1 device, taken through the axis of the coil. Fig. 3 is a transverse sectional view of the Fig. 1 device, taken along the line 33 of Fig. 1.

Referring now to Fig. 1, it will be noted that the principal supporting element of our tuned coil is a socalled Tiunerman nut 10 which consists of a metal stamping formed to provide a cap portion 10a, having a central aperture, and a pair of opposed side portions 1% which are bent into a generally cylindrical form below cap portion llla. In addition, Tinnerman'nut 10 is provided with a pair of additional downwardly extending Wings 100 which are pressed into the same cylindrical outline defined by Wings 1%.

Wings 1% terminate at their lower ends in a pair of lugs 11 which are bent outwardly away from the wing members 1012.

The central aperture is cap member 10a is suitably threaded, as by force-threading, to receive a machine screw 12, suitably slotted at its upper end 13 to permit convenient rotation by means of a screw driver. The lower end of screw 12 is not threaded, but is provided with an annular shoulder 12a, to be more fully described hereinafter.

Tinnerman nut 10 is crimped or pressed-fitted onto serves as a high-Q tuning element.

may be made tighter and more secure by providing a pair of slots 16 in the sides of tube 14 where they may receive tabs 17 formed by stamping in the side wings 10b of cap nut 10.

Sleeve 14 is provided with an inwardly extending dimple 18 at any desired point; in the embodiment illustrated, we have placed dimple 18 at the same radial position in tube 14 as is occupied by slot 15. This construction is convenient, but if desired dimple 18 may be located elsewhere.

Carried within brass sleeve 14 is a coil form 21 made of any desired type of insulating material, such as poly styrene or-ceramic. The upper portion of coil form 21 is machined to provide a smoothly sliding fit within sleeve 14. The lower portion of coil form 21, however, is annularly undercut to provide a recessed surface on which one or more inductance coils 22 may be wound.

In the form of the'invention shown, we have shown only a single coil 22; this is a matter of design, however, and if a double-tuned coupling transformer is de-' sired, a pair of coils may be wound on form 21 with their respective turns interlaced.

The lower terminal of coil 22 may be secured to coil form 21 by cementing or any other desired means. Coil 22 may conveniently be terminated at its upper end by passing the wire into axial slot 21a and hence downward along tube 21 under the turns of coil 22, so that the wire terminal lead 22a will pass externally of the coil at the lower end of coil form 21.

Slot 21a preferably extends the full length of coil form 21, and form 21 is so oriented within brass sleeve 14 that slot 21a receives within it the inwardly protruding portion of dimple 18, as shown in Fig. 3.

Screw 12 is axially received within the upper end of coil form 21 in a manner such that the screw may turn within the coil form but cannot be withdrawn because of engagement between the material of the coil form 21 and annular shoulder 12a. This arrangement is most easily accomplished by molding the coil form 21 around the lower end of screw 12, the molding pressure used being sufficiently low to leave screw 12 free to rotate within coil form 21. a

In operation, our tuning device may be inserted'through a chassis hole of suitable size and secured in place by any convenient means as, for instance, by friction contact, by soldering, or by riveting the lugs 11 to the chassis. Thus mounted, the tuning device will have its upper end, including the top of screw 13, extending above the chassis, While the remainder of the device will lie below the chassis where external circuit connections can readily be made to the terminals of the coil or coils 22.

The brass sleeve 14, in addition to housing coil 22, It operates in this manner: When screw 13 is turned by means of a suitable screw driver, the coil form 21, carrying coil 22, will move upward or downward, depending on the direction of rotation. (It will be understood that dimple 18 will prevent rotation of coil form 21.) As the coil 22 is moved axially relative to sleeve 14, the inductive field of coil 22 is varied in magnitude. The slot 15 keeps down the magnitude of the eddy currents in sleeve 14, so that the Q of the combined coil and sleeve remains high. If the form 21 be designed to provide substantial clearance between the coil 22 and the sleeve 14, slot 15 may not be required.

It will be understood, of course, that sleeve 14 need not be made of brass. It can be made of any conducting material, although non-magnetic materials are to be preferred.

This little tuning device, it will be found, is capable of extraordinarily goodperformance at a cost almost unbelievably low.

It will of course be understood that many changes can be made in the details of construction of our invention without departing from its spirit. For example, the effect of the dimple 18 in preventing relative rotary motion between the sleeve and the coil form may be accomplished in many other Ways. Thus the aperture 27 and the corresponding'aperture in cap a which holds sceW 13 may be oriented slightly off-center, or the cross section of the sleeve and coil form may be made noncircular.

While we have in this specification described in considerable detail a typical embodiment of our invention, it is to be understood that the scope of the invention is to be determined primarily by reference to the appended claims.v

We claim:

1. A radio frequency tuning device, comprising a generally cylindrical coil form made of insulating material, said form having first and second opposite cylindrical end portions with a step therebetween, said second portion being reduced in diameter relative to said'first portion, a coil wound on said second portion of said form, said coil having a diameter corresponding generally to that of said first portion of said form, a conductive metal generally cylindrical inductance varying sleeve slidably receiving said form and coil, said first portion of said form being closely received within said sleeve to guide said sleeve, said form being slidable axially into and out of said sleeve so that said sleeve will selectively envelop said coil and thereby varythe inductance thereof, said sleeve and said form having respective interengaging elements restraining said sleeve and form against relative rotation While permitting relative axial movement thereof, an elongated rod, said form having an axial aperture therein rotatably receiving one end of said rod, said rod and said form having respective interengaging shoulder elements restraining said rod and form against relative axial movement While permitting relative rotation thereof, said rod having an externally threaded portion on its opposite end, and an internally threaded closure element on one end of said sleeve threadedly receiving saidexternally threaded portion of said rod whereby rotation of said rod will effect relative axial 4 movement of said coil and said sleeve and thereby will vary the inductance of said coil.

2. A radio frequency tuning device, comprising a cylindrical coil form made of insulating material, said form having first and second opposite cylindrical end portions with a step therebetween, said second portion being reduced in diameter relative to said first portion, a coil wound on said second portion of said form, said coil having a diameter corresponding generally to that of said' first portion of said form, a conductive metal cylindrical inductance varying sleeve slidably receiving said form and coil, said first portion of said form being closely received within said sleeve to guide said sleeve, said form being slidable' axially into and out of said sleeve so that said sleeve will selectively envelop and thereby vary the inductance thereof, said sleeve having a longitudinal slot therein to minimize eddy current losses therein, said sleeve having an inwardly extending key element thereon, said form having a longitudinal key slot therein receiving said key element to restrain said sleeve and form against relative rotation while permitting relative axial movement thereof, an elongated cylindrical rod, said formhaving an axial aperture therein rotatably receiving one end of said rod, said rod and said form having respective interengaging annular shoulder elements restraining said rod and form against relative axial movement While permitting relative rotation thereof, said rod having an externally threaded portion on its opposite end, and a' cap" on one end of said sleeve and having an internally threaded axial opening threadedly receiving said externally threaded portion of said rod whereby rotation of said rod willelfectrelative axial movement of said coil and said sleeve and thereby will vary the inductan'ce of said coil.

References Cited in the file of this patent- UNITED STATES PATENTS.

1,042,855 Walker Oct. 29, 1912 2,403,349 Dolberg July 2, 1946 2,423,824 Beetham July 15, 1947 2,503,100 Dewhurst et a1, Apr. 4, 1950 2,534,854 Clapp Dec. 19, 1950 I FOREIGN PATENTS 338,263 Italy Mar. 31, 1936 

